Bidirectional hydrodynamic shaft seal

ABSTRACT

A shaft seal of the bidirectional hydrodynamic type with flutes that meet the sealing band or lip edge tangentially, the flutes being continuous and providing for hydrodynamic return of oil that has leaked past the lip edge. The continuous flutes are readily and accurately provided during molding in a seal having an as-molded lip edge.

United States Patent 1 June 27, 1972 Berens [54] BIDIRECTIONALHYDRODYNAMIC SHAFT SEAL [72] Inventor: Alfred S. Berens, Farmington,Mich.

[731 Assignee: Federal-Mogul Corporatlon, Southfield,

Mich.

[22] Filed: May25,1970

[21] Appl.No.: 40,144

52 U.S.Cl .Q ..277/134 [51] lnt.Cl ...Fl6jl5/32 [58] FieldofSearch..277/l34 [56] References Cited UNITED STATES PATENTS 3,561,770 2/1971Corsi ..277/l34X 1,811,588 6/1931 2,446,380 8/1948- 2,985,551 11/19603,504,918 4/1970 Halliday ..277/134 Primary Examiner-Samuel B. RothbergAttorney-Owen, Wickersham & Erickson [5 7] ABSTRACT A shaft seal of thebidirectional hydrodynamic type with flutes that meet the sealing bandor lip edge tangentially, the flutes being continuous and providing forhydrodynamic return of oil that has leaked past the lip edge. Thecontinuous flutes are readily and accurately provided during molding ina seal having an as-molded lip edge.

8 Claims, 11 Drawing Figures PATENTEDJM? 1972 3. 672.690

SHEET1UF4 FIG. 2

FIG. 3

INVENTOR. ALFRED S. BERENS E WJ/M ZQAH ATTORNEYS PATENTEDJUH 27 1972 sum3 or 4 INVENTOR. ALFRED S. BERENS 0w, MM 544 ATTORNEYS PATENTEDJUNZ?1912 SHEET U 0F 4 INVENTOR. ALFRED S. BERENS ATTORNEYS BIDIRECTIONALHYDRODYNAMIC SHAFT SEAL This invention relates to bidirectionalhydrodynamic shaft seals. Such seals are exemplified by US. Pat. Nos.3,504,918; 3,504,919 and 3,504,920, issued to George Angus and Company,Limited. Basically, these seals are shaft seals of the lip type havingan outer (air side) frustoconical surface that is provided with helicalridges, grooves, or flutes which obliquely meet the sealing band or lipedge in opposite peripheral directions, respectively, at a small angle,not more than 20 and preferably between 1 and to provide a fluidfeedback effect in either direction of shaft rotation.

The seal exemplified by the recently issued patent can be made to do itsjob well, but it is rather critical in its operations. When the sealstructure is sought to be made by trimming the lip, there areinaccuracies which cannot be tolerated except where the shaftinterference can be quite large. Consequently, it is preferable to formthe sealing band or lip edge as an asmolded surface. This createsspecial problems, both in the construction of the mold and in theresulting seal.

For example, in one type of bidirectional hydrodynamic seal havingflutes, several flutes are molded in the approach surface of the seal soas to obliquely intersect the sealing or contact band, sometimes knownas the static band. The mold may be made in the conventional mannerexcept for the grooves required to form the flutes or ribs. The groovesmay be formed by turning in a lathe, in which the die member is rotatedabout an axis slightly oblique to its own longitudinal axis. Thecircular grooves so turned, and, the resulting molded ridges, aremutually parallel, and the centers of their circles are successivelyoffset from the axis of the frustoconical surface. Under this prior artdesign one or more of these grooves intersects with the trim line of theseal. The finished trimmed seals thus have one or more ribs intersectingthe static lip or primary lip in two opposite circumferentialdirections, each individual rib intersecting the lip once in eachdirection. Where there is a plurality of ribs, they intersect theprimary lip successively in one direction and successively in theopposite direction. A similar seal may be made by cutting a series ofgrooves in the mold so that each groove is radially spaced from theother so as to produce an alternating pattern of intersections with theprimary lip, first in one direction and then the opposite direction andcontinually alternating. Where the seal lips are to be trimmed, suchstructure presents no problem to a skilled mold maker. However,molded-lip molds are much more difficult to make, since the prior artgrooves cannot, in that fonn of structure be continuous. The mold cornerrequired to produce the molded primary lip interferes with anycontinuous milling or cutting operation.

While two-piece molds or cores can be made, they are expensive and arenot fully satisfactory in production. Whether the joint be bolted,brazed, or otherwise held together, that joint between the two pieces ofthe mold tends to leak rubber, resulting in unacceptable flash at theprimary lip, also known as the sealing band.

The present invention provides a seal structure particularly suitable tothe formation of as-molded lips that are satisfactory and also haveas-molded bidirectional hydrodynamic flutes.

A basic feature of the invention is that the hydrodynamic ribs or flutesthat reach the primary lip are tangent to the sealing band or lip edgerather than intersecting it. This configuration enables the flutes tomeet the sealing band or primary lip obliquely in opposing directionsand provides a hydrodynamic effect in either direction of shaftrotation. The configuration also enables the use of a one-piece moldcore, which is easily made by a skilled machinist, since the flutes donot extend beyond the mold corner and, being continuous, they can be cutor milled on a lathe in a continuous operation.

Other objects and advantages of the invention will appear from thefollowing description of some preferred forms thereof.

In the drawings:

FIG. 1 is a view in perspective of a shaft seal embodying the principlesof the invention, a portion of the case being broken away.

FIG. 2 is a fragmentary enlarged view in elevation and partly in sectionof the lip portion of the shaft seal of FIG. 1.

FIG. 3 is a developed view of the surface of the complete innerperiphery of the seal of FIGS. 1 and 2.

FIG. 4 is a view similar to FIG. 3 of a modified form of seal having aplurality of flutes.

FIG. 5 is an enlarged view in elevation and in section of the lipportion showing one form of flute structure.

FIG. 6 is a view similar to FIG. 5 of a modified form of lip structure.

FIG. 7 is a view similar to FIG. 5 of another modified form of lipstructure.

FIG. 8 is a view similar to FIG. 5 of another modified form of lipstructure.

FIG. 9 is a view similar to FIG. 5 of yet another modified structureembodying the principles of the invention.

FIG. 10 is a partial view of the seal of FIG. 9 looking at FIG. 9 fromthe right.

FIG. 11 is a fragmentary developed view of another modified fonn of sealhaving several parallel flutes.

In the seal of FIGS. 1 to 3 the shaft seal 10 comprises a metalreinforcing member 11 provided with a suitable boresealing cylindricalsurface 12 either of metal or of elastomer coating on the metal. Aradially inwardly extending flange 13 is used to provide an anchorportion 14 to which an elastomeric body 15 is molded and bonded. Thisbody 15 comprises a lip 16 and has a spring receiving groove 17 for asuitable garter spring 18. The lip 16 is the intersection of twoconvergent frustoconical surfaces 20 and 21, the surface 20 facingtowards and the surface 21 away from the fluid sealing or oil side ofthe seal 10. The seal 10 as shown in FIG. 2 has not been completed,though a trim line 22 is indicated; instead, the body 15 is shown in oneof its possible as-molded shapes, in which there is a hat-like portion23 that is to be trimmed off but is formed during the molding by theflow of excess elastomer. FIG. 2 thus shows how the seal 10 can bemolded so that the primary lip 16 or sealing band is defined in the moldas the meeting point of the frustoconical surfaces 20 and 21. Thesealing band 16 is continuous and is co-axial with the molded body 15and the cylindrical case surface 12. It may be termed the static sealinglip or primary lip of the seal. This lip is generally of the kindpresent in most shaft seals, and its formation and shape may berelatively conventional.

The invention differs from conventional seals by its use of at least oneflute 25, to provide a bidirectional dynamic seal, in other words, toreturn across the sealing band 16 any oil or other liquid which hasmanaged to leak across the sealing band 16, whether due to a defect inthe sealing band 16 itself or in the shaft on which it seals. As can beseen from FIGS. 1 to 3, the flute 25 meets the sealing band 16 andleaves it tangentially. It does not cross the sealing band 16. It iscontinuous and therefore lies at a variable angle relative to the lip16, but it is easily provided on a mold, for example, by a lathe. Beingtangent at just one point 26, it is evident that at this point thebidirectional principle is operating, so that depending on the directionof rotation, either the portion 27 of the flute 25 leading into thetangency 26 or that portion 28 which leaves the tangency 26 is operatingas the hydrodynamic member to return the fluid.

While the single-flute structure. shown in FIGS. 1 to 3 is satisfactoryfor some uses, better results are obtained if there is a plurality offlutes, such as is shown in the developed view of FIG. 4, in which asingle line represents each flute. In this view there are threedifferent flutes 30, 31, and 32 which meet the sealing band 16 attangencies 33, 34, and 35, and the points of tangency are made to besubstantially equally spaced around the seal, so that there are threepoints 33, 34, and 35 at which hydrodynamic action is retained in eitherdirection of rotation, there being, in effect, six action points withonly three of them in operation at any one time, depending on therotational direction of the shaft relative to the seal.

It is also possible, as shown in FIG. 11, to have several parallelflutes, 100, 101, 102, each represented by a single line, the leadingflute being tangent to the narrow seal lip or band 16. In that instanceonly the tangent flute 100 is active when the seal is new, but one ormore in each of the parallel groups becomes active as the seal wears andthe sealing band 16 widens, as shown in FIG. 11 by the shaded portion.Thus, the flute 101 eventually becomes hydrodynamically operative.Further wear results in the flute 102 becoming active, and so Variousconfigurations of the individual flutes or ribs are feasible as shown inFIGS. -8, in which the flutes are shown greatly enlarged in size ascompared with the rest of the seal. Thus, in FIG. 5 each flute 40 isformed by a projecting rib 41, which projects out from the normallyfrustoconical air side 21 of the seal and, due to the fact that itprojects back at an angle, preferably of five to ten degrees, itprovides a cavity or groove-like portion having one surface 42 thatsubstantially follows the normal frustoconical shape 21 and anothersection 43 that meets that at a line 44, preferably at an obtuse angle,though it may meet at a different angle if desired.

FIG. 6 shows a somewhat similar form in which each flute 50 is formed bya wall 51 that in the as-molded shape projects directly radially andanother wall 52 that is cylindrical, i.e., parallel to the surface ofthe shaft on which it is to seal. It meets a portion 53 of the wall 21at a line 54. When this seal is put on the shaft, the shaft interferencechanges the angle and at some portions makes it approach somewhat theshape of the groove of FIG. 5. It will be understood, of course, thatthis section is taken in just one position and that at another positionthe shape would approach very close to the sealing lip or band 16.

FIG. 7 shows another form of seal with a groove 60 in which a surface 61of the projecting rib 62 lies substantially parallel to the oil side ofthe seal and forms a groove between it and a portion 63 the normallyfrustoconical air side 21, which it intersects at a line 64.

FIG. 8 shows yet another form of seal of this invention in which a rib71 that forms a flute 70 is substantially hemispherical, as a projectionbeyond the normal frustoconical surface 21. Here, again, a groove isformed between this hemispherical head 71 and a portion 72 of the normalfrustoconical wall 21, the bead 71 and portion 72 intersecting at a line73. When provided according to the showing in FIGS. 1 through 3,duopositive hydrodynamic sealing is again obtainable.

A further refinement, which is desirable to establish an unbroken orcontinuous lip when the seal is new, is to have one flute concentricwith the seal lip, as shown in FIGS. 9 and 10. The flute 80 preferablyhas the same cross section as the hydrodynamic flute and at no pointdoes it have a smaller diameter than the smallest hydrodynamic flutediameter. This insures simultaneously a leak-free static seal and anactive hydrodynamic action. FIG. 9 shows the sealing band, or lip edge16 and a concentric flute 80. There, as previously described, one ormore oblique flute 81 is tangent to the con centric flute 80. The mostdesirable practice would be to cut this concentric flute in the moldafter generating the hydrodynamic flutes therein. As shown in FIG. 10,as the section A-A is moved around the circumference toward AA theoblique flute 81 moves toward the static flute 80, as shown by thedotted flutes of FIG. 9, until at AA, the static and dynamic flutes 80and 81 exactly coincide. As a result, the sections AA and AA areidentical, and both look like FIG. 9. The letters A, B, C, D, E, and F,show in both views to give an identification of elements.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. A shaft seal comprising a molded sealing ring of resilient materialhaving a peripheral sealing lip with inner and outer mutuallyconvergent, generally frustoconical surfaces respectively facing towardsand away from the fluid-sealing side of the seal,

a continuous circumferential sealing band co-axial with said ring anddefined by the convergence of said frustoconical surfaces,

said outer frustoconical surface having a plurality of hydrodynamicflutes, each flute being continuous and tangentially meeting saidsealing band once only and tangentially leaving it once only, saidflutes crossing each other, with their points of tangency being evenlyspaced around said sealing band, said flutes being operative when theshaft is rotating relative to the seal in either direction to sweep backto said sealing band fluid that leaks past said sealing band.

2. The shaft seal of claim 1 wherein there is in addition at least onemore continuous flute parallel to and spaced axially from each saidcontinuous flute and having a larger diameter, so that as the sealingband wears, said one more flute becomes hydrodynamically active in placeof the former flute and whereby there is a plurality of groups ofparallel said flutes, with their actual and prospective points oftangency evenly spaced around said sealing band.

3. A bidirectional hydrodynamic shaft seal comprising,

a rigid annular member, and

a molded sealing member of elastomeric material supported by and bondedto said rigid annular member, said sealing member having a primarysealing lip for making circular contact with a shaft rotating relativelyto said lip, said lip having a side that faces the liquid to be sealedand an air side that faces away from the sealed fluid,

said air side having a generally frustoconical approach surface andhaving therein a plurality of continuous dynamic flutes projecting fromsaid surface and spaced axially from each other and transversely obliqueto the plane of said primary lip, a plurality of said dynamic fluteseach meeting and leaving said lip tangentially at one single locus oftangency to provide hydrodynamic action when the seal is mounted on arotating shaft, whichever is the direction of rotation.

4. The seal of claim 3 wherein each dynamic flute is accompanied by atleast one parallel flute of somewhat larger diameter to become active asthe seal wears.

5. The shaft seal of claim 3 wherein each said dynamic flute provides afrustoconical surface inclined to the plane of said primary lip at anangle of 3 to 7 and meeting said approach surface at an obtuse angle,the portion of each said dynamic flute that tangentially meets andleaves said lip coming into contact with the shaft and cooperatingtherewith and with said approach surface to define a wedge that trapsleaked oil and returns it across said lip.

6. The shaft seal of claim 5 wherein each said flute is about 0.010 to0.020 inch wide.

7. A shaft seal comprising a molded sealing ring of resilient materialhaving a peripheral sealing lip with inner and outer mutuallyconvergent, generally frustoconical surfaces respectively facing towardsand away from the fluid sealing side of the seal,

a continuous circumferential sealing band co-axial with said ringdefined on said lip by the convergence of said frustoconical surfaces,

said outer frustoconical surface having a continuous static fluteparallel to and spaced from said sealing band and a plurality ofcontinuous hydrodynamic flutes, each tangentially meeting said staticflute and tangentially leaving it, at a single locus of tangency withtheir respective points of tangency evenly spaced around said staticflute,

said static flute having its inner diameter no smaller than the smallestinner diameter of said hydrodynamic flute,

said hydrodynamic flutes being operative when the shaft is rotatingrelative to the seal in either direction to sweep back to said sealingband fluid that leaks past said sealing band.

8 The shaft seal of claim 7 wherein said static flute and saidhydrodynamic flutes are identical in shape.

1. A shaft seal comprising a molded sealing ring of resilient materialhaving a peripheral sealing lip with inner and outer mutuallyconvergent, generally frustoconical surfaces respectively facing towardsand away from the fluid-sealing side of the seal, a continuouscircumferential sealing band co-axial with said ring and defined by theconvergence of said frustoconical surfaces, said outer frustoconicalsurface having a plurality of hydrodynamic flutes, each flute beingcontinuous and tangentially meeting said sealing band once only andtangentially leaving it once only, said flutes crossing each other, withtheir points of tangency being evenly spaced around said sealing band,said flutes being operative when the shaft is rotating relative to theseal in either direction to sweep back to said sealing band fluid thatleaks past said sealing band.
 2. The shaft seal of claim 1 wherein thereis in addition at least one more continuous flute parallel to and spacedaxially from each said continuous flute and having a larger diameter, sothat as the sealing band wears, said one more flute becomeshydrodynamically active in place of the former flute and whereby thereis a plurality of groups of parallel said flutes, with their actual andprospective points of tangency evenly spaced around said sealing band.3. A bidirectional hydrodynamic shaft seal comprising, a rigid annularmember, and a molded sealing member of elastomeric material supported byand bonded to said rigid annular member, said sealing member having aprimary sealing lip for making circular contact with a shaft rotatingrelatively to said lip, said lip having a side that faces the liquid tobe sealed and an air side that faces away from the sealed fluid, saidair side having a generally frustoconical approach surface and havingtherein a plurality of continuous dynamic flutes projecting from saidsurface and spaced axially from each other and transversely oblique tothe plane of said primary lip, a plurality of said dynamic flutes eachmeeting and leaving said lip tangentially at one single locus oftangency to provide hydrodynamic actiOn when the seal is mounted on arotating shaft, whichever is the direction of rotation.
 4. The seal ofclaim 3 wherein each dynamic flute is accompanied by at least oneparallel flute of somewhat larger diameter to become active as the sealwears.
 5. The shaft seal of claim 3 wherein each said dynamic fluteprovides a frustoconical surface inclined to the plane of said primarylip at an angle of 3* to 7* and meeting said approach surface at anobtuse angle, the portion of each said dynamic flute that tangentiallymeets and leaves said lip coming into contact with the shaft andcooperating therewith and with said approach surface to define a wedgethat traps leaked oil and returns it across said lip.
 6. The shaft sealof claim 5 wherein each said flute is about 0.010 to 0.020 inch wide. 7.A shaft seal comprising a molded sealing ring of resilient materialhaving a peripheral sealing lip with inner and outer mutuallyconvergent, generally frustoconical surfaces respectively facing towardsand away from the fluid sealing side of the seal, a continuouscircumferential sealing band co-axial with said ring defined on said lipby the convergence of said frustoconical surfaces, said outerfrustoconical surface having a continuous static flute parallel to andspaced from said sealing band and a plurality of continuous hydrodynamicflutes, each tangentially meeting said static flute and tangentiallyleaving it, at a single locus of tangency with their respective pointsof tangency evenly spaced around said static flute, said static flutehaving its inner diameter no smaller than the smallest inner diameter ofsaid hydrodynamic flute, said hydrodynamic flutes being operative whenthe shaft is rotating relative to the seal in either direction to sweepback to said sealing band fluid that leaks past said sealing band. 8.The shaft seal of claim 7 wherein said static flute and saidhydrodynamic flutes are identical in shape.